If a food or similar product in which a piece of vinyl, metal or similar foreign object is mixed is shipped to the market, the trustworthiness of the product will be noticeably lowered. Accordingly, in factories or similar facilities, a contamination inspection of the product is performed. If a foreign object is found in the inspection of the product, the foreign object is analyzed to determine the kinds, amounts and other properties of the contained substances or elements. The foreign object is subsequently identified by using a reference object database to reveal its origin and mixture route.
An analyzing device that is suitable for an analysis of a piece of vinyl or similar foreign object made of an organic substance is the Fourier transform infrared spectrometer (FTIR). In the FTIR, the foreign object is irradiated with interference waves generated by a Michelson interferometer including fixed and movable mirrors, and the transmitted or reflected light is measured as an interferogram. By Fourier-transforming this interferogram, an absorption spectrum is obtained, with the horizontal axis representing the wavenumber and the vertical axis representing the intensity (e.g. absorbance or transmittance). On the absorption spectrum, infrared absorptions appear at the wavelengths corresponding to the amounts of vibration energy or rotation energy of various substances contained in the foreign object. Accordingly, by comparing the absorption spectral pattern of the foreign object with those of the various reference objects previously stored in the reference object database, the foreign object can be identified from the similarity of the contained substances (for example, see Patent Literature 1).
On the other hand, an analyzing device that is suitable for an analysis of a piece of metal or similar foreign object which contains an inorganic substance is the energy dispersive fluorescent X-ray analyzer (EDX). In the EDX, the foreign object is irradiated with X-rays to obtain a fluorescence spectrum. On this fluorescence spectrum, an X-ray fluorescence peak appears at a specific energy position to each element. Accordingly, it is possible to identify an element contained in the foreign object by determining the peak position on the fluorescence spectrum. The quantity of the identified element can be determined by two methods: the FP method (fundamental parameter method) and the calibration curve method. In the FP method, the quantitative value of each element is determined by reproducing the measured intensity of the X-ray fluorescence using a theoretical formula with an assumed composition of the principal components (for example, see Patent Literature 2 or 3). As compared to the calibration curve method which requires preparing a calibration curve by measuring a plurality of standard samples having the same composition and known content, the FP method is advantageous in that such a task is unnecessary and the analysis can be easily performed. Quantitative values determined by the FP method are commonly called “semi-quantitative values” to distinguish them from exact quantitative values determined by the calibration curve method. By comparing the semi-quantitative values of the elements in the foreign object determined by the FP method with those of the elements contained in the various reference objects previously stored in the reference object database, the foreign object can be identified from the similarity of the contained substances.